GUIYANG - An initial investigation has revealed that the fatal explosion in Southwest China's Guizhou province on Tuesday was caused by two trucks loaded with explosives that were illegally parked and failed to transport their cargo in the proper fashion, local authorities said Wednesday.

The death toll from the explosion climbed from seven to eight on Wednesday, as a bystander who was seriously injured in the blast died in a hospital, according to publicity officials from the city of Fuquan, where the blast occurred.

A total of 218 injured are hospitalized to receive treatment, nine of whom are in critical condition.

The incident occurred when one of the two cargo trucks, loaded with about 70 metric tons of explosives, blew up in front of a motor vehicle testing station on Tuesday morning in Fuquan, about 100 km from Guizhou's capital of Guiyang, according to the local rescue headquarters.

The two vehicles belonged to a local transportation company in Fuquan, according to the investigation.

Windows were shattered in nearby houses, and cars parked near the site were severely damaged. A nearby grain warehouse was also seriously damaged.

More than 6,000 students from six nearby schools have had their classes suspended, as the schools were damaged by the explosion, according to officials from the municipal education bureau.

The Ministry of Public Security has dispatched experts from Henan and Hunan provinces to participate in a probe of the accident.

Nineteen medical experts and 170 medical personnel, along with 50 ambulances, were dispatched to the site of the explosion at the request of the Ministry of Health.

The city government has earmarked 5 million yuan ($787,065) to relocate people whose houses were damaged in the explosion, as well as cover their medical treatment.